The invention relates to the manufacture of anhydrous isopropyl alcohol suitable for fuel purposes.
The catalytic hydration of olefins in the gaseous phase at elevated temperature, elevated pressure and a molar water-to-olefin ratio of 0.5-1:1 has long been known. Phosphoric acid applied to a variety of support materials has proven to be an especially good catalyst for this purpose. Support materials involved are, for example, silicic acid, silicates, diatomaceous earth, aluminum silicates, etc.
The alcohols made in accordance with known catalytic hydration processes are used as solvents and for reactional as well as other special purposes. They have to be free of by-products, which necessitates expensive refinement. Thus, the crude alcohol produced in the synthesis must first be treated in columns where it is extracted by washing, and then refined, rectified and dried (dewatered) in four additional columns. Furthermore, for the removal of the water a foreign withdrawing agent (benzine/benzene, cyclohexane) must be used in order to remove the alcohol-water azeotrope.
It is known that isopropyl alcohol is an excellent fuel component due to its high octane number, its solubility in water, its engine-cleaning action and especially its exhaust-improving properties. Pure isopropyl alcohol as described above, however, in spite of its extremely attractive properties, has been used rarely or not at all in fuels for Otto-cycle engines, since it proves to be non-economical.